Multiplex communication system



R .J. VA

F. C. P. HENROTEAU MULTIPLEX COMMUNICATION SYSTEM March 3,1942.

Filed March 5, 1941 Patented Mar. 3, 1942 UNITED STATES PATENT OFFICEFrancois Charles Pierre Hcnroteau, Ottawa, I v Ontario,-CanadaApplication March 5, 1941, Serial No. 381,906

g In Belgium March 6, 1940 3 Claims.

This invention relates to multiplex communication systems and is adevelopment from the apparatus described in my prior United Statesapplication Ser.No. 252,030 filed January 20, 1939.

The system of the present invention comprises a central station and anumber of substations so arranged that wireless communication may be hadsimultaneously and on the same wave length between the central stationand all or some of the substations, and it may be used for example in anaval or aerial squadron to permit communication between the squadroncommanders unit and other units.

The underlying idea of the invention is that may be synchronizedand thatthe selection by a substation of the signals intended for it or thetransmission from that station of a signal for the central stationwithout overlapping with signals prises a central station including anenvelope operations at the central station and substations containing anumber of mosaics (the term mosaic meaning wherever used in thisapplication an assembly of the type used in many television systems andconsisting of a multiplicity of mutually insulated tiny conductiveelectron emissive elements and a uniformly conductive backing layer, theelements and this layer often being carried on a central dielectricplat-e), means for scanning said mosaics simultaneously by differentslow moving electron releasing beams and means for scanning said mosaicssuccessively by a single fast moving electron releasing beam in a timeno greater than that elapsing during the scanning of one mosaic by oneof the slow moving beams, and a number of substations no greater thanthe number of mosaics at the central station and each including anenvelope. the envelope at each different substation containing onlyasingle mosaic corresponding in position to a different mosaic at thecentral station. means for scanning each single mosaic by a slow movingelectron beam synchronously with the scanning by the slow movingelectron beams at the central station, and means for scanning eachsingle mosaic by a fast moving electron beam synchronously with thescanning of the mosaic at the central station with which it correspondsin position by the first mentioned fast moving electron beam. Thecentral station and each substation preferably includes a transmitterand a receiver so that two way communication is possible. In such a casean envelope forms part of each transmitter and each receiver. In thetransmitter each slow moving electron beam is modulated by beamsreconstitute the message or messages from the record or records soformed, In order to prevent beats due to phase displacement of thecarrier wave coming in to the receiver at the central stationsimultaneously from the emitters at a number of central stations. meansare preferably provided at each of the latter to prevent transmission ofthe carrier wave except while it is modulated by a message. Theinvention will now be described in more detail by reference to theaccompanying drawing of one suitable form". In the drawing-- I Figure 1is the transmission at the central station;

Figure 2 is the receiver at the central station; Figure 3 is thereceiver at a substation, and Figure 4 is the transmitter at asubstation. The transmitter of Figure l is similar to the transmittershown in Figure l of my prior application and comprises an envelope Icontaining three mosaics 4. 5 and 6 having a common central dielectric pate 3 and a common conductive backing connected through an appropriateamplifying and modulating device I4 to an emitting antenna l5.Associated with the mosaics is a conventional electron gun I housed in apocket in the envelope. At the other end of the envelope and facing themosaics is an electron emissive plate 8 which has three electron guns94. 95 and 96 associated with it, each including a modulating electrodel0 connected to, for example, a microphone Between the plates is anaccelerating electrode !2 and inside the envelopean electronic lens inthe form of a coudensive coil IS.

The receiver of Figure 2 is similar to the transmitter of Figure 1 butwith the'clccf-ron guns reversed and the conductive bookings of themosaics separate. Thus. electron guns l4. l5 and 16 are associated withthe mosaics 4|, 5| and BI respectively and the conductive backing ofeach mosaic is connected through an appropriate amplifying device 18with, for example, a pair of earphones l9. On the other hand oneelectron gun 9 is associated with the plate BI and its modulatingelectrode I is connected through an appropriate demodulator andamplifier IS with areceiving antenna 11.

At each substation the transmitter may .be identical with thetransmitter at the central sta tion except that there is only one mosaicand only one electron gun associated with the electron emissive plate.Figure 4 shows the transmitter for one substation. Here there is amosaic 4a corresponding in position to the mosaic 4 in Figure 1,;andmounted conveniently on a plate 3a identical with the plate 3 in Figure1 and there is one electron gun 94a, corresponding to the gun 94 ofFigure 1, associated with the plate 8a identical with the plate 8 inFigure 1.

Similarly, the receiver at each substation may be identical with thereceiver at the central station except that there is only one mosaic andassociated electron gun. Thus in Figure 3; which shows the receiver forthe substation of which the transmitter is shotm in Figure 4, there isOnly a mosaic lla corresponding in position to the mosaic H of Figure 2,and an associated electron gun Ma. As in Figure 4, the mosaic isconveniently on a plate 31a identical with the plate 3! of Figure 2.

Each of the two other substations, which a system having the centralstation transmitter .and receiver of Figures 1 and 2 could include,

would have the same receiver and transmitter as those shown in Figures 3and 4 except that the mosaics would correspond in position with themosaics 5i and 5 and 4| and 4 respectively.

The system described operates generally as described in my priorapplication in connection with the contemporaneous transmission of anumber of messages over a single transmission channel. In Figure l, theslow-moving electron beams from the guns S4. 95 and 98 are caused toscan simultaneously different areas of the plate 8 corresponding to themosaics 4, 5 and 6 respectively, the intensity of these beams beingmodumosaic Ma. It thus leaves a record only of the signalling impulsescorresponding to the message impressed on the beam of the gun 94 andrecorded on the mosaic 4. The mosaic Ma is scanned by a slow-moving beamof electrons from the gun Ida synchronously with the scanning by thebeam from the gun 94 and thus reconstitutes the message which passes tothe earphones. At the receivers of the other two sub- I stations onlythe messages recorded on the mosaics 5 and 6 respectively arereconstituted. Thus although all the messages are sent on the same wavelength from the central station, each substation efiectively receivesonly the message intended for it.

In a similar way in the transmitter of Figure 4, a slow-moving beam ofelectrons from the gun 94a. modulated in accordance with the message tobe sent to the central station scans an area of the plate 8acorresponding to the area of the plate 8 scanned by the beam of the gun94 synchronously with that beam, and so produces a slow-moving beam ofsecondary electrons which scans the mosaic 4a and records the message onit. The record on the mosaic is translated into signalling impulses bythe fast-moving beam from the gun 7a scanning the mosaic synchronouslywith the scanning by the beam from the gun l at the central station. Atthe transmitters at the other substations scanning proceeds.synchronously with the scanning in the transmitter of Figure 4, butthese other substations have only mosaics corresponding in position tothe mosaics 5 and 6 respectively at the central station with the resultthat the formation of signalling impulses begins for example in thesecondsubstation only after such formation has -.at the receiver of thecentral station picks up successively the signally impulses coming fromlated by the modulating electrodes ID in accordance with messages to betransmitted. When one of the beams 94, 95 and 96 strikes the plate setof earphones is through the amplifiers It.

these beams causes beams of secondary electrons moving beam of electronsfrom the gun I in a time at the most equal to the time taken for onescanning of a mosaic by the above mentioned beams of secondaryelectrons. and this scanning converts the records into signallingimpulses with which a carrier wave is modulated and transmitted. At thesubstation shown in Figure 3 the receiving antenna picks up all thesignalling impulses transmitted from the central station, and theintensity of the fast-moving electron beam from the gun 9a. which. scansthe plate 8la synchronously with the scanning of the plate 3 by the beamfrom the gun I at the emitter, is modulated in accordance with them.

The arrangement shown in Figures 3 and 4 where the mosaics 4a and Ma areon plates identical respectively with the plates 0 and 3! struction ofthe apparatus. since an easy way is There is thus produced a beam ofsecondary electrons of variable intensity which scans the plate 3|a butleaves a record only during a part 0! this scanning, namely, when ittraverses the mission from the antenna l5a except when sig- I nailingimpulses are being produced in order to prevent at the receiver thebeats which would otherwise be caused by phase. displacement between thewaves received from the different substations. A convenient arrangementfor this purpose is shown in Figure 4 where the conductive backing forthe mosaic 4a is connected to the filament 20 of a three electrode tube2| to the plate 22 of which the antenna is connected.

cathode ray oscillograph 25 containing a plate I 26 having an electronemissive area 21 having the same relative position on the plate as themosaic 4a on the plate 3a. The plate is scanned by a beam of electronssynchronously with the scanning by .the beam from the gun la. When thesurface 21 is scanned there is an emission of electrons which beingpicked up by the anode 24 causes the grid 23 to acquire a potential suchas to allow passage of current through the tube 2l but when the rest ofthe surface 26 is scanned the potential of the grid 23 is such as toblock any passage of current and thus prevent transmission from theantenna l5a.

The invention has been described with relation to one particular form ofconstruction but it will be understood that it is not limited to formthus for example, it can perfectly well be used with the alternativeform of construction shown in my prior application referred to.Moreover, it is not essential that scanning of the mosaics by the slowmoving and fast moving electron beams proceed simultaneously since thismight be effected alternatively as indicated in my prior application,

What I claim is:

mosaic at the central station, means for scanning each single mosaic bya slow moving electron, The grid 23 is connected to an anode 24 of abeam synchronously with the scanning by the slow moving electron beamsat the central station, and means for scanning each single mosaic by afast moving electron beam synchronously with the scanning of the mosaicat the central station with which it corresponds in position by thefirst mentioned fast moving electron beam.

2. A multiplex communication system according to claim 1 in which ateach substation the slow moving electron releasing beam is adapted torecord a message On the single mosaic and the fast moving beam toconvert the record into signalling impulses, comprising means formodulating a carrier wave by said impulses, and means for preventingtransmission of such wave except 1. A multiplex communication systemcomprising a central station including an envelope containing a numberof mosaics, means for scanning said mosaics simultaneously by differentslow moving electron releasing beams and means for scanning said mosaicssuccessively by a single fast moving electron releasing beam in a timeno greater than that elapsing during the scanning of one area by one ofthe slow moving beams, and a number of substations no greater than thenumber of mosaics at the central station and each including an envelope,the envelope at each diiferent substation containing only a singlemosaic corresponding in position to a different when so modulated.

3. A multiplex communication system according to claim 1, in which ateach substation the slow moving electron releasing beam is adapted torecord a message on the single mosaic and the fast moving beam toconvert the record into signalling impulses, comprising means for modu--lating a carrier wave by said impulses, and means for preventingtransmission of such wave except when so modulated, said last mentionedmeans comprising a three electrode tube having a filament to which saidcarrier wave is fed, a plate connected to an antenna and a grid normallyat a potential such as to prevent passage of electrons from saidfilament to said plate, and an auxiliary tube having an electronemissive plate in a position therein corresponding to the posi tion ofthe single mosaic in the envelope connected to said grid, and means forscanning said plate with an electron releasing beam synchronously withthe scanning of the mosaic in the envelope at the substation by the fastmoving electron releasing beam. FRANCOIS CHARLES PIERRE HENRO'I'EAU.

